/*
 * Copyright 2007 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package fi.jasoft.qrcode.zxing;

/**
 * <p>
 * A simple, fast array of bits, represented compactly by an array of ints
 * internally.
 * </p>
 * 
 * @author Sean Owen
 */
public final class BitArray {
    private int[] bits;
    private int size;

    public BitArray() {
        this.size = 0;
        this.bits = new int[1];
    }

    public BitArray(int size) {
        this.size = size;
        this.bits = makeArray(size);
    }

    public int getSize() {
        return size;
    }

    public int getSizeInBytes() {
        return (size + 7) >> 3;
    }

    private void ensureCapacity(int size) {
        if (size > bits.length << 5) {
            int[] newBits = makeArray(size);
            System.arraycopy(bits, 0, newBits, 0, bits.length);
            this.bits = newBits;
        }
    }

    /**
     * @param i
     *            bit to get
     * @return true iff bit i is set
     */
    public boolean get(int i) {
        return (bits[i >> 5] & (1 << (i & 0x1F))) != 0;
    }

    /**
     * Sets bit i.
     * 
     * @param i
     *            bit to set
     */
    public void set(int i) {
        bits[i >> 5] |= 1 << (i & 0x1F);
    }

    /**
     * Flips bit i.
     * 
     * @param i
     *            bit to set
     */
    public void flip(int i) {
        bits[i >> 5] ^= 1 << (i & 0x1F);
    }

    /**
     * Sets a block of 32 bits, starting at bit i.
     * 
     * @param i
     *            first bit to set
     * @param newBits
     *            the new value of the next 32 bits. Note again that the
     *            least-significant bit corresponds to bit i, the
     *            next-least-significant to i+1, and so on.
     */
    public void setBulk(int i, int newBits) {
        bits[i >> 5] = newBits;
    }

    /**
     * Clears all bits (sets to false).
     */
    public void clear() {
        int max = bits.length;
        for (int i = 0; i < max; i++) {
            bits[i] = 0;
        }
    }

    /**
     * Efficient method to check if a range of bits is set, or not set.
     * 
     * @param start
     *            start of range, inclusive.
     * @param end
     *            end of range, exclusive
     * @param value
     *            if true, checks that bits in range are set, otherwise checks
     *            that they are not set
     * @return true iff all bits are set or not set in range, according to value
     *         argument
     * @throws IllegalArgumentException
     *             if end is less than or equal to start
     */
    public boolean isRange(int start, int end, boolean value) {
        if (end < start) {
            throw new IllegalArgumentException();
        }
        if (end == start) {
            return true; // empty range matches
        }

        int endInt = end - 1;
        int firstInt = start >> 5;
        int lastInt = endInt >> 5;
        for (int i = firstInt; i <= lastInt; i++) {
            int firstBit = i > firstInt ? 0 : start & 0x1F;
            int lastBit = i < lastInt ? 31 : endInt & 0x1F;
            int mask;
            if (firstBit == 0 && lastBit == 31) {
                mask = -1;
            } else {
                mask = 0;
                for (int j = firstBit; j <= lastBit; j++) {
                    mask |= 1 << j;
                }
            }

            // Return false if we're looking for 1s and the masked bits[i] isn't
            // all 1s (that is,
            // equals the mask, or we're looking for 0s and the masked portion
            // is not all 0s
            if ((bits[i] & mask) != (value ? mask : 0)) {
                return false;
            }
        }
        return true;
    }

    public void appendBit(boolean bit) {
        ensureCapacity(size + 1);
        if (bit) {
            bits[size >> 5] |= (1 << (size & 0x1F));
        }
        size++;
    }

    /**
     * Appends the least-significant bits, from value, in order from
     * most-significant to least-significant. For example, appending 6 bits from
     * 0x000001E will append the bits 0, 1, 1, 1, 1, 0 in that order.
     */
    public void appendBits(int value, int numBits) {
        if (numBits < 0 || numBits > 32) {
            throw new IllegalArgumentException(
                    "Num bits must be between 0 and 32");
        }
        ensureCapacity(size + numBits);
        for (int numBitsLeft = numBits; numBitsLeft > 0; numBitsLeft--) {
            appendBit(((value >> (numBitsLeft - 1)) & 0x01) == 1);
        }
    }

    public void appendBitArray(BitArray other) {
        int otherSize = other.getSize();
        ensureCapacity(size + otherSize);
        for (int i = 0; i < otherSize; i++) {
            appendBit(other.get(i));
        }
    }

    public void xor(BitArray other) {
        if (bits.length != other.bits.length) {
            throw new IllegalArgumentException("Sizes don't match");
        }
        for (int i = 0; i < bits.length; i++) {
            // The last byte could be incomplete (i.e. not have 8 bits in
            // it) but there is no problem since 0 XOR 0 == 0.
            bits[i] ^= other.bits[i];
        }
    }

    /**
     * 
     * @param bitOffset
     *            first bit to start writing
     * @param array
     *            array to write into. Bytes are written most-significant byte
     *            first. This is the opposite of the internal representation,
     *            which is exposed by {@link #getBitArray()}
     * @param offset
     *            position in array to start writing
     * @param numBytes
     *            how many bytes to write
     */
    public void toBytes(int bitOffset, byte[] array, int offset, int numBytes) {
        int boffset = bitOffset;
        for (int i = 0; i < numBytes; i++) {
            int theByte = 0;
            for (int j = 0; j < 8; j++) {
                if (get(boffset)) {
                    theByte |= 1 << (7 - j);
                }
                boffset++;
            }
            array[offset + i] = (byte) theByte;
        }
    }

    /**
     * @return underlying array of ints. The first element holds the first 32
     *         bits, and the least significant bit is bit 0.
     */
    public int[] getBitArray() {
        return bits;
    }

    /**
     * Reverses all bits in the array.
     */
    public void reverse() {
        int[] newBits = new int[bits.length];
        for (int i = 0; i < this.size; i++) {
            if (get(this.size - i - 1)) {
                newBits[i >> 5] |= 1 << (i & 0x1F);
            }
        }
        bits = newBits;
    }

    private static int[] makeArray(int size) {
        return new int[(size + 31) >> 5];
    }

    public String toString() {
        StringBuffer result = new StringBuffer(size);
        for (int i = 0; i < size; i++) {
            if ((i & 0x07) == 0) {
                result.append(' ');
            }
            result.append(get(i) ? 'X' : '.');
        }
        return result.toString();
    }

}